T_{2k} := \left\{ \displaystyle\frac{(-1)^{2k} + 2\cdot 2k}{2k \sin\left( \frac{(-1)^{2k - 1}\pi}{2} \right)} : k \in \mathbb{N} \right\} = \left\{ -2 - \displaystyle\frac{1}{2k} : k\in\mathbb{N} \right\}